Spark plug shield



HALLETT 2,358,972

SPARK PLUG 5 HI ELD Filed Jan. 19, 1943 A4 F/QED 564M577,

TEXTUR Patented Sept. 26, 1944 SPARK PLUG SHIELD Alfred Hallett, Los

Angcles, Callt, assignor to Hallett Manufacturing Company, Inglewood, CaliL, a copartnership Application January 19, 1943, Serial No. 472,900

6 Claims.

This invention relates to the art of shielding the ignition system of an internal combustion engine, and particularly to a new and improved form of shielding for the spark plugs thereof.

Unshielded elements of an ignition system in proximity to radio receivin apparatus cause interference with radio reception. The high tension currents of the system normally cause the greatest difllculty, and in the case of airplanes, motor boats, and land vehicles seriously diminishes the utility of the radio receiving apparatus.

By enclosing the various elements of the ignition system within a metallic housing which is grounded, the electrical radiations from the system will be dissipated into the ground and the interference eliminated. In .the case of spark plugs themselves they have been shielded by building a metallic housing into the plug itself which is expensive and not otherwise fully satisfactory. I am also aware of a separate spark plug housing but the one with which I am familiar is complicated and renders the spark plugs dimcult of access, as well as having other faults which I have eliminated by my invention.

It is an object of my invention to provide a spark plug shielding of light weight, simple construction and readily assembled or disassembled, and which nevertheless serves the function of a shielding with maximum efiiciency.

Another object of my invention is to provide a means for circulation of air through the spark plug shield. This is important because ozone is generated by electrical currents which in the close confinement of tight shielding combines with air to form nitric acid, a highly objectionable condition. By causing a circulation of air through the shielding, the ozone is removed and the formation of a deleterious acid is reduced to a minimum.

These and other objects of my invention will be made more apparent from a further consideration of the disclosure.

In the drawing: I

Figure l is an elevational View of my spark plug shield shown in its relation to a spark plug installed in the cylinder wall of an internal combustion engine.

Figure 2 is a vertical cross sectional view taken on the line 2-2 of Figure l.

Figure 3 is a perspective enlarged view' of a novel form of conductor terminal sleeve which appears in section in Figure 2.

My spark plug shield is indicated by the reference numeral II) illustrated as enclosing a spark plug II which is installed in a cylinder head I2 of an internal combustion engine.

The spark plug shield which is sometimes referred to in the trade as a can comprises an enlarged tubular member l3 oi suflicient diameter to provide a space I4 between the tubular member and the hexagonal shoulder I5 of the spark plug to accommodate a conventional spark plug socket wrench. The lower portion of the tubular member I3 is reduced as illustrated at I6 to closely confine the cylindrical extension I1 of the spark plug. The extreme lower end of the tubular member I3 is turned in to form a flange I8 adapted to be clamped between the lower end of the spark plug extension I! and a conventional gasket I9.

Toward the lower end of the tubular member I3 is a small hole 20 for the reception of air as more particularly hereinafter described.

Near the upper end of the tubular member I3 is formed an internal annular ledge or shoulder 2| upon which rests a flange 22 of an insulating member 23. The tubular member I3 is threaded externally at its upper end as illustrated.

The insulating member 23 is formed with an inverted frusto conical cavity 24 calculated to provide a space separating the insulator from the porcelain 25 of the spark plug and the terminal 26 thereof. The insulator also provides effective insulation between the spark plug terminal and the walls of the tubular member I3 as well as the superstructure of the spark plug can hereinafter described. This insulator shown and terminates in a cylindrical extension 21.

threaded ring 34 serves to clamp the parts together as illustrated.

tapers upwardly as ecu A high tension conductor 3'6 covered with insulation 3% ends within a fiber sleeve 31, in the lower end region of which is securely fastened a metallic terminal plate 38 having a hollow stem be into which the end of the cable 35 is introduced and preferably soldered. The stem carries a small flange id which serves to retain the upper end of a terminal spring 4i, the lower portion of the latter enclosing and making contact with the terminal 25 of the spark plug.

The fiber sleeve 37 should be of lesser external diameter than the internal diameter of the insulator extension 27? whereby an air passage therebetween is provided.

The upper end of the sleeve 31 is formed with diametrically opposed slots 62 to provide air passages from the upper end of the insulator section 2? into the region above as subsequently described.

A ferrule 56 which may be formed as a part of or is welded to the lower end of a tubular housing at is adapted to rest at offset points upon the upper end of the fiber sleeve 31 and the upper end of the element 32, being drawn down by means of a threaded collar 41. The internal diameter of the ferrule 35 is less than the external diameter of the cable insulation 36 to provide an air passage t8.

The fiber sleeve 31 as well as the insulator 23 both serve the function of insulators. The tubular member iii, the conical element 30, the ring 36, and the parts 45, 4B, and M are made of a metal which is a good electrical conductor. The tubular housing 56 will normally be grounded at its opposite end, not illustrated, and the gasket is is of a soft metal such as copper, so that the shield is grounded to the engine at the spark plug end.

In use, the shield may be assembled with the spark plug in the following manner: The spark plug is introduced into the open tubular member i3 and threaded into the cylinder wall. The in= sulato'r 23 is then placed in position, the gasket laid in place, the member 30 put on and tightened down by the collar 36. The cable terminal including the sleeve 371 is then inserted and the collar ii tightened to complete the assembly.

The shield may be disassembled by removing the two threaded collars 3E and 57. Access to the spark plug for inspection, cleaning, or changing is thus made simple and convenient.

The cable terminal is quickly attached to the spark plug or detached, adequate insulation at critical points is established, and there is an air passage from the hole 26 through the assembled shield communicating with the interior of the tubular cable housing 56. This passage is attributable in substantial measure to the novel form of fiber sleeve 37 in which the slots 32 provide communication which would otherwise be obstructed by engagement of the ferrule with the upper end of the sleeve.

The hole 28 is not large enough for drops of moisture to pass through, and the shield is thus virtually a weatherproof physical protection to the spark plug in addition to its function as an electrical shielding.

By connecting the tubular housing 36 to any suitable air exhaust, as for example, the intake manifold or carbureter of the engine, a circulation of air through the spark plug shield and its cable connections may be maintained.

Although I have herein shown and described my invention in what I have conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of my invention. which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

By the term "metallic" in the claims, I refer not only to metal which is a good electrical conductor, but intend to include any material which is a good conductor, or a material treated or coated in such a manner as to render it conductive.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a device of the character described, a metallic housing adapted to enclose a spark plug and to be grounded therewith, said housing having an upper portion substantially reduced above the spark plug terminal, a cable housing detachably Joined to the end of said upper portion, and a cable terminal disposed in said upper portion and having an air passage through said terminal between the-spark plug housing and the cable housing.

2. In a device or the character described. a metallic housing adapted to enclose a spark plug and to be grounded therewith, said housing having an upper portion substantially reduced above the spark plug terminal, a cable housing having a ferrule adapted to seat upon the end of said upper portion, means to secure the ferrule to the said upper portion, a cable terminal comprising an insulating sleeve the upper end of which is adapted to be snugly engaged by the ferrule, said sleeve being formed with a port to provide an air passage through the sleeve for communication between the housing and the cable housing.

3. In a device of the character described, a metallic housing adapted to enclose a spark plug and to be grounded therewith, said housing having an upper portion substantially reduced above the spark plug terminal, a cable housing having a ferrule adapted to seat upon the end of said upper portion, means to secure the ferrule to the said upper portion, a cable terminal comprising an insulating sleeve the upper end of which is adapted to be snugly engaged by the ferrule, said sleeve being formed with a port to provide an air passage through the sleeve for communication between the housing and the cable housing, and the housing having means for the entry of air.

4. A device of the character described comprising: a metallic spark plug housing adapted to shield a spark plug and including a lower section having a lower end flange adapted to be interposed between the spark plug base and the wall of the engine in which the spark plug is installed and the upper end being open and suitable for the reception of a socket wrench, an upper section adapted to be detachably coupled to the lower section and which is reduced at its upper end, a cable housing providing an air passage between the housing and a cable therein and adapted to be detachably coupled to the said upper section, an insulator nesting in the housing and having an extension entering the reduced portion of the upper housing section, and a cable terminal including an insulating sleeve extending within the said insulator extension but spaced therefrom to provide an air passage, said sleeve having air passages at its upper end whereby complete air communication is provided between said spark plug housing and said cable housing.

5. A device of the character described comprising: a metallic spark plug housing adapted to shield a spark plug and including a lower section hevi a lower end flange adeptecl to be inter oo tween the spark plug bese end the well of .318 in which the spark plug is installed end being open and sluteble for c cption of a socket Wrench, an upper secto be cletechebly coupled to the low which is reduced at its upper end, sing adapted to be detachably coupled upper section, an insulator nesting i lug housing and having on exten ring the reduced portion of the upper l'lousiin, section, and a cable terminal including inslnetlng sleeve extending within the said insulatol. extension, the spark plug housing having 1 for the entry of air, anal pawage said sleeve communicating between the interior of the spark plug housing and the cable housing.

6. In a device of the character described, a metallic housing adapted to enclose a spark plug and to be grounded therewith, said housing hav ing an upper portion substantially reduced above spark plug terminal, a ceble housing having e ferrule adapted to seat upon the upper end of said upper portion, a threaded collar to secure the ferrule to said upper portion, and a cable terminal comprising an insulating sleeve the upper end of which is adapted to be snugly engaged by the ferrule and said cable terminal including means at the lower end to rest upon and make electrical connection with a spark plug.

ALFRED 

